1. Field of the Invention
The invention discloses novel series of silicone esters which are useful as antioxidants on skin. The products are produced using for a variety of hydroxyl containing actives such as vitamin A (retinol), vitamin A-2, and vitamin E. Compounds of the invention are prepared by the esterification of (a) a specific silicone methyl ester and (c) a hydroxyl functional active. The esters of the present invention allow for the formulation of personal care products in which the “active” can be formulated into a variety of solvents without the loss of activity.
By hydroxyl, functional active is meant a vitamin, co-vitamin, or other material known to effect a change to the hair or skin, which contains a hydroxyl group or hydroxyl groups.
2. Arts and Practices
The personal care market is a very diverse market segment, which includes a number of products designed to protect the skin and hair from the degradation effects of sunlight and environmental distress caused by free radicals.
In addition to protecting the hair and skin by acting as antioxidants, there is a need for products that improve the condition of the hair, skin nails, and lips. The desirable functions include but are not limited to; barrier properties, remoisturization, softening, and conditioning.
One of the most important functions of human skin is the protection against adverse environmental factors. Environmental factors like exposure of the skin to sun, cold or heat adversely affects the skin and minimizes the barrier property of the skin. Additionally, the application of many cosmetic products or use of soap on the skin removes the fatty layer of the skin. It is therefore highly desirable to replace the barrier properties, which are removed from the skin. Lipids and other oily materials added to the skin improve the natural barrier properties of the skin and hair the skin retain moisture and feel soft. If a suitable delivery system is used Vitamin A, Vitamin A-2, and Vitamin E are excellent materials for use as moisturizing and barrier créme applications. These materials are very difficult to deliver from aqueous environment. One attempt to deliver these materials to the skin has been to make emulsions of these oils in water. This is done by selecting surface-active agents, which will emulsify the hydroxyl active into small droplets, which are surrounded by the surface-active agent in what are called micelles. The resulting emulsion resembles milk and contains the emulsified hydroxyl active. The difficulty with this approach is that the material present in the micelle is deposited very inefficiently onto the hair and skin since the micelle must break to deliver the oil. Since the majority of the micelles do not break, the majority of the active is rinsed off and ends up in the drain. Another approach has been to make derivatives of these oily materials. There has therefore been a long felt need for materials, which could be incorporated into personal care products, which deliver vitamins to the skin.
We have discovered that the incorporation of Vitamin A, Vitamin A-2, and Vitamin E, into a silicone ester in relatively low concentrations results in polyesters which can be made soluble in many different solvents and which give the beneficial properties of the cholesterol or lanolin to the skin and hair. In short, low concentrations of these esters by virtue of their substantivity to hair and skin will provide outstanding protection from oxidation and free radical attack as well as moisturizing properties in many varied personal care formulations. Activity is seen at as low as 0.1%.
U.S. Pat. No. 5,210,133 to O'Lenick Jr., issued May 1993 discloses “novel series of silicone polyesters which are useful as delivery systems for a variety of hydroxyl containing active such as lanolin, cholesterol, dihydrocholesterol, Vitamin A, Vitamin D-2, Vitamin D-3, Vitamin D-4, Vitamin E, and panthenol.
These undesirable by-products alter the properties of the compound. The cross-linked silicone molecule can cause gellation of the product. The vitamin cross-linked to another vitamin lacks water solubility and therefore results in products, which split into two phases. These problems have resulted in lack of commercial success of the products. It was not until the current invention was it understood that the reaction of a silicone methyl ester with the hydroxyl vitamin that clear homogeneous cosmetically acceptable products could be produced that do not split into two phases.